ZINC ARSENITE AS AN INSECTICIDE.* 



W. J. SCHOENE. 



SUMMARY. 



This is a report of a series of experiments with zinc arsenite and 

 lead arsenate to determine their relative toxicity to insects and the 

 safeness of zinc arsenite for use on foliage. 



One pound of zinc arsenite proved equal in effectiveness to three 

 pounds of lead arsenate. 



Zinc arsenite when added to calcium hydrate or bordeaux mixture 

 caused no injury to apple foliage; but more or less spotting of apple 

 leaves occurred when the poison was used singly or in combina- 

 tion with lime-sulphur or glucose. Zinc arsenite alone or with 

 glucose caused severe burning of grape foliage. Laboratory tests 

 suggest that the injury to foliage by zinc arsenite may be due in 

 part to the solubility of the poison in carbonic acid. 



The contradictory results from the use of zinc arsenite on foliage 

 suggest that the poison as manufactured is not a stable or uniform 

 product. 



Zinc arsenite or lead arsenate with bordeaux, soap or glue con- 

 tinued effective for twenty-five days. Either of the poisons alone 

 or with glucose gradually lost its poisonous properties on exposure 

 to weather and by the end of this period had ceased to protect the 

 foliage. 



Incidental to the main problem it appears in these tests that the 

 lime-sulphur solution does not resist wet weather as well as 

 bordeaux mixture. 



INTRODUCTION. 



Zinc arsenite has recently been introduced as an insecticide and 

 has been advertised for sale in this State. The chief advantages 

 claimed for the poison are that it has a high arsenical content and 

 is in a form readily available to insects. On the basis of the pre- 

 vailing market prices it is, besides, more economical than arsenate 

 of lead, which at the present is largely used in spraying operations 

 against leaf-eating and fruit-eating insects. The experiments herein 

 reported were planned to determine by field and laboratory tests 

 its rate of action as compared with arsenate of lead, and its safeness 



* Keprint of Technical Bulletin No. 28, March, 1913. 



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